In 1963, on their way home from the hospital after he was born, Louis Rozzo’s parents stopped by a building on Ninth Avenue in Chelsea, where the family ran a wholesale seafood business, to weigh him in a scallop scale. This March, when virtually every restaurant, club and hotel that bought seafood from him closed and his firm’s income dried up in a matter of days, Mr. Rozzo went back to where it all began.

The F. Rozzo & Sons building was still in the family. Mr. Rozzo converted the ground floor into a makeshift store where he sells clams, scallops, sea bass and American red snapper to people who are suddenly cooking at home a lot more than they used to.

“I’m seeing people taking home fish, then coming in the next day and showing me pictures of how they prepared it,” he said. Some of them undertake recipes that require the better part of a day. Mr. Rozzo enjoys their enthusiastic feedback, although he also suggested that some of the energy New Yorkers are devoting to their kitchen projects is, like his overnight fish store itself, born of desperation.